Problem: Determine where $f(x)$ intersects the $x$ -axis. $f(x) = (x + 9)^2 - 16$
Explanation: The function intersects the $x$ -axis where $f(x) = 0$ , so solve the equation: $ (x + 9)^2 - 16 = 0$ Add $16$ to both sides so we can start isolating $x$ on the left: $ (x + 9)^2 = 16$ Take the square root of both sides to get rid of the exponent. $ \sqrt{(x + 9)^2} = \pm \sqrt{16}$ Be sure to consider both positive and negative $4$ , since squaring either one results in $16$ $ x + 9 = \pm 4$ Subtract $9$ from both sides to isolate $x$ on the left: $ x = -9 \pm 4$ Add and subtract $4$ to find the two possible solutions: $ x = -5 \text{or} x = -13$